Highest streak I can remeber is a 15 killstreak on s1, I found a great camp spot for s1 though so Ima try that out, and Ima snipe to make it legit till I run outta ammo 
on s1 i had a 23 KS till sum1 found my spotdude masterclip i got 19 on s1 try and beat that...next i'm going for is 25